Apparatus and method for analyzing mode change of unidirectional composite materials

This application claims a benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 10-2022-0038500 filed on Mar. 29, 2022, on the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.

The present disclosure relates to a method and device for analyzing mode change of a unidirectional composite material. More particularly, the present disclosure relates to a method and device for analyzing mode change of a unidirectional composite material, wherein the method and the device are capable of observing change in a modal parameter of a material whose structural stiffness is reinforced in a specific direction.

A composite material refers to combination of different kinds of materials and has properties that may not be obtained from a single material. Unlike a single material, the composite material may not be uniform in terms of a microstructure and may not be continuous and may have multiphases. The composite material may be largely divided into particle reinforced materials, fiber reinforced materials, and structural composite materials.

The composite material has physical or chemically enhanced properties compared to the single material. Light and strong composite material may be produced. However, physical properties of the composite material are greatly affected by a structure of the material or a type of the material.

A carbon-based composite material (CBC material) is used in various industrial fields due to its high stiffness and damping quality. For example, a carbon fiber reinforced material is light and strong, and is used in fields requiring weight reduction, such as aerospace and automobile fields.

However, a structure of the carbon-based composite material using carbon fibers changes depending on an orientation of the carbon fiber. Thus, the structural stiffness or damping quality of the composite material is dominantly influenced by the carbon fiber. For example, dynamic behavior of the carbon fiber reinforced material may change due to the anisotropic nature of the material depending on the carbon fiber. Thus, a resonance frequency and a mode shape thereof change. Further, the structural stiffnesses of a composite structure having the same shape is reinforced in varying directions, such that the mode shape thereof changes due to the influence of the stiffness reinforcing direction. In the prior art, it may be identified that modal parameter information change depending on whether the structural stiffness is reinforced or the direction in which the structural stiffness is reinforced. However, there is a problem in that how a parameter corresponding to an order of a mode of interest changes cannot be specifically examined.

A prior art related to the present disclosure includes Japanese Patent Application Publication No. 2015-032295 (2015.02.16)

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify all key features or essential features of the claimed subject matter, nor is it intended to be used alone as an aid in determining the scope of the claimed subject matter.

A purpose of the present disclosure is to provide a method and device for analyzing mode change of a unidirectional composite material, wherein the method and device can examine change in a modal parameter of a material whose structural stiffness is reinforced in a specific direction.

A purpose of the present disclosure is to provide a method and device for analyzing mode change of a unidirectional composite material, wherein the method and device can minimize shape information change of each mode caused by structural stiffness reinforcing and can effectively examine change of each mode using a modal assurance criterion (MAC).

A purpose of the present disclosure is to provide a method and device for analyzing mode change of a unidirectional composite material, wherein the method and device can predict dynamic behavior when the structural stiffness is reinforced in a specific direction even without fabricating a specimen and testing the same.

Purposes in accordance with the present disclosure are not limited to the above-mentioned purpose. Other purposes and advantages in accordance with the present disclosure as not mentioned above may be understood from following descriptions and more clearly understood from embodiments in accordance with the present disclosure. Further, it will be readily appreciated that the purposes and advantages in accordance with the present disclosure may be realized by features and combinations thereof as disclosed in the claims.

A first aspect of the present disclosure provides a method for analyzing change in a mode of a unidirectional composite material, the method comprising: applying a physical force of a predetermined pattern onto one side of a unidirectional composite material specimen; sensing a vibration signal generated by the physical force at at least one sensed position of the specimen; performing modal analysis of a frequency response at a corresponding measurement location, based on the physical force applied to the specimen and the vibration signal measured at the sensed position of the specimen, and calculating at least one mode shape vector of the specimen based on the modal analysis result; compensating the calculated mode shape vector based on a distance between a normal line passing through a center of the structure of the specimen and the sensed position, thereby calculating a modified mode shape vector; and calculating a first modal assurance criterion (MAC) of the specimen based on the modified mode shape vector.

In one implementation of the first aspect, the specimen includes a unidirectional carbon-based composite structure (UCBC) whose structural stiffness is reinforced in a single direction of an angle θ.

In one implementation of the first aspect, the specimen includes the unidirectional carbon-based composite structure (UCBC) whose structural stiffness is reinforced in a single direction of one of 0 degree, 30 degrees, 45 degrees, 60 degrees and 90 degrees.

In one implementation of the first aspect, performing the modal analysis of the frequency response includes calculating a frequency response function using a following Equation 1 based on the physical force applied to the specimen and the vibration signal measured at the sensed position of the specimen:

In one implementation of the first aspect, calculating the modified mode shape vector includes: calculating a distance vector of a following Equation 2 based on the distance between the at least one sensed position and the normal line; and calculating a normalized distance vector using a following Equation 3:

In one implementation of the first aspect, calculating the modified mode shape vector includes calculating the modified mode shape vector using a following Equation 4 based on the normalized distance vector:φ=((φ)·diag({circumflex over ()}))  [Equation 4]

In one implementation of the first aspect, calculating the first modal assurance criterion of the specimen using the modified mode shape vector includes calculating the first modal assurance criterion using a following Equation 5:

In one implementation of the first aspect, calculating the first modal assurance criterion of the specimen using the modified mode shape vector includes calculating the first modal assurance criterion between the modified mode shape vector of the specimen and a mode shape vector of an isotropic material, based on the modified mode shape vector of the specimen and the mode shape vector of the isotropic material.

In one implementation of the first aspect, the method further comprises calculating a second modal assurance criterion of the specimen using a following Equation 6 based on the mode shape vector calculated via the modal analysis of the frequency response:

In one implementation of the first aspect, calculating the second modal assurance criterion of the specimen includes calculating the second modal assurance criterion between the mode shape vector of the specimen and a mode shape vector of an isotropic material, based on the mode shape vector of the specimen and the mode shape vector of the isotropic material.

A second aspect of the present disclosure provides a device for analyzing change in a mode of a unidirectional composite material, the device comprising: a vibration exciter configured to set a vibration excitation pattern under control, and apply a physical force to one side of a unidirectional composite material specimen according to the set vibration excitation pattern; a sensor for measuring a vibration signal generated at the specimen due to the physical force at at least one sensed position of the specimen; a modal analyzer for performing modal analysis on a frequency response at a corresponding measurement position based on the physical force applied to the specimen and the vibration signal measured at the sensed position of the specimen, and calculating at least one mode shape vector of the specimen based on the modal analysis result; a modified mode shape vector calculator for compensating the mode shape vector calculated by the modal analyzer to calculate a modified mode shape vector; and a first modal assurance criterion calculator for calculating a first modal assurance criterion (MAC) based on the calculated modified mode shape vector, wherein the modified mode shape vector calculator is configured to compensate the mode shape vector calculated by the modal analyzer based on a distance between a normal line passing through a center of the structure of the specimen and the sensed position, thereby calculating the modified mode shape vector.

In one implementation of the second aspect, the first modal assurance criterion calculator is configured to calculate the first modal assurance criterion using a following Equation 7:

In one implementation of the second aspect, the device further comprises a second modal assurance criterion calculator configured to calculate a second modal assurance criterion of the specimen based on the mode shape vector calculated by the modal analyzer.

In one implementation of the second aspect, the second modal assurance criterion calculator is configured to calculate the second modal assurance criterion using a following Equation 8:

As described above, the method and device for analyzing mode change of the unidirectional composite material can examine change in a modal parameter of a material whose structural stiffness is reinforced in a specific direction.

Further, the method and device for analyzing mode change of the unidirectional composite material can minimize shape information change of each mode caused by structural stiffness reinforcing and can effectively examine change of each mode using a modal assurance criterion (MAC).

Moreover, the method and device for analyzing mode change of the unidirectional composite material can predict dynamic behavior when the structural stiffness is reinforced in a specific direction even without fabricating a specimen and testing the same.

When it is guaranteed that an influence of the reinforcing of the structural stiffness of a given composite structure in a specific direction on the mode shape is linear, the method and device for analyzing the mode change of the unidirectional composite material according to the present disclosure may also be effective in predicting the dynamic behavior of the composite structure whose the structural stiffness is reinforced in a plurality of directions.

In addition to the effects as described above, specific effects in accordance with the present disclosure will be described together with the detailed description for carrying out the disclosure.

For simplicity and clarity of illustration, elements in the drawings are not necessarily drawn to scale. The same reference numbers in different drawings represent the same or similar elements, and as such perform similar functionality. Further, descriptions and details of well-known steps and elements are omitted for simplicity of the description. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure. Examples of various embodiments are illustrated and described further below. It will be understood that the description herein is not intended to limit the claims to the specific embodiments described. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the present disclosure as defined by the appended claims.

A shape, a size, a ratio, an angle, a number, etc. disclosed in the drawings for illustrating embodiments of the present disclosure are illustrative, and the present disclosure may not be limited thereto. The same reference numerals refer to the same elements herein. Further, descriptions and details of well-known steps and elements are omitted for simplicity of the description. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present disclosure. As used herein, the singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise”, “comprising”, “include”, and “including” when used in this specification, specify the presence of the stated features, integers, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, operations, elements, components, and/or portions thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expression such as “at least one of” when preceding a list of elements may modify the entirety of list of elements and may not modify the individual elements of the list. When referring to “C to D”, this means C inclusive to D inclusive unless otherwise specified.

It will be understood that, although the terms “first”, “second”, “third”, and so on may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section described below could be termed a second element, component, region, layer or section, without departing from the spirit and scope of the present disclosure.

It will be understood that when an element or layer is referred to as being “connected to”, or “coupled to” another element or layer, it may be directly on, connected to, or coupled to the other element or layer, or one or more intervening elements or layers may be present. In addition, it will also be understood that when an element or layer is referred to as being “between” two elements or layers, it may be the only element or layer between the two elements or layers, or one or more intervening elements or layers may also be present.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In one example, when a certain embodiment may be implemented differently, a function or operation specified in a specific block may occur in a sequence different from that specified in a flowchart. For example, two consecutive blocks may be actually executed at the same time. Depending on a related function or operation, the blocks may be executed in a reverse sequence.

In descriptions of temporal relationships, for example, temporal precedent relationships between two events such as “after”, “subsequent to”, “before”, etc., another event may occur therebetween unless “directly after”, “directly subsequent” or “directly before” is not indicated.

The features of the various embodiments of the present disclosure may be partially or entirely combined with each other, and may be technically associated with each other or operate with each other. The embodiments may be implemented independently of each other and may be implemented together in an association relationship.

Hereinafter, a method and device for analyzing the mode change of the unidirectional composite material according to the present disclosure will be described.

is a configuration diagram showing a configuration of a device for analyzing the mode change of the unidirectional composite material according to an embodiment of the present disclosure.

Referring to, a devicefor analyzing the mode change of the unidirectional composite material may include a vibration exciter, a sensor, and a mode change analyzer. The mode change analyzermay include a modal analyzer, a modified mode shape vector calculator, a first modal assurance criterion (MCA) calculator, and a second modal assurance criterion calculator.